The present invention relates to the general technical field of domestic electrical appliances designed for steam cooking.
In general terms, steam cookers have a cooking enclosure associated with a water reservoir, the water in the reservoir being heated to produce steam serving to cook the foodstuffs contained in the cooking enclosure. Electric steam cooking appliances have an electric heating means, or element for producing steam from the water in the reservoir.
When the water has reached its boiling point, steam is produced in large quantities. An electric steam cooking appliance having high heating capacity has the advantage of reaching boiling point quickly, and producing steam in large quantities. However, some of the steam may then not be used for heating the foodstuffs. The result is a more or less significant output of steam outside the appliance, as well as a loss of energy.
The patent document GB 2 198 631 discloses the use of a steam detector for reducing the heating power, so as to avoid production of excessive steam. One drawback of the appliance described in this document lies in the fact that the steam reaches the steam detector without having passed through the cooking enclosure. Thus the reduction in the heating power does not take account of the foodstuffs present in the cooking enclosure. Another drawback of the appliance described in this document lies in the fact that the heating element is disposed in the main water reservoir. As a result, the rate of increase of the temperature of the water contained in the reservoir remains limited even with a high heating power, and the production of steam takes a long time to occur.
The present invention provides a domestic electrical appliance for steam cooking which reconciles effective cooking with a limitation of the discharge of steam outside the appliance.
The present invention also provides a domestic electrical appliance for steam cooking of the aforementioned type, which is economical to make.
The present invention further provides a domestic electrical appliance for steam cooking of the aforementioned type which is easy to use.
A domestic electrical appliance for steam cooking according to the invention comprises: a steam production device that includes a water reservoir and heating means for heating water in the reservoir; a cooking enclosure associated with the steam production device to be supplied with steam by the steam production device, the cooking enclosure having at least one exhaust to the outside; a steam detector; control means operatively associated with the steam detector for reducing the rate of heat generation by the heating means; and a descending conduit that communicates between the cooking enclosure and the steam detector for directing a flow of steam from the cooking enclosure to the steam detector.
Tests have shown that, during cooking, an offset in time exists between the appearance of a high flow of vapor, or steam, in the appliance and the exit of a significant steam output from the appliance. This is because, at the start of cooking, the foodstuffs begin by absorbing the steam to a major extent, and their temperature increases. As long as the foodstuffs are absorbing a major part of the steam produced, the excess quantities of steam leave the cooking enclosure without difficulty through the exhaust or exhausts. When the surface temperature of the foodstuffs approaches the temperature of the steam, the ability of the foodstuffs to absorb the heat from the steam decreases, and the quantity of steam escaping from the cooking enclosure tends to increase.
However, when the excess quantities of steam increase, the exhaust or exhausts limit the discharge rate. The steam must then descend through the conduit in order to reach the detection zone of the detector for controlling the reduction in power of the heating element. Because of this, the steam which has reached the cooking enclosure does not immediately reach the detector. The cooking can therefore continue at full power for a longer period, which improves the effectiveness of the appliance.
In a second step, the steam flow generated at reduced power supplies the energy necessary for continuing the cooking, without excessive losses.
Compared with an appliance that continuously supplies a reduced heating power, the duration of cooking is reduced in an appliance according to the invention. The ejection of steam to the outside is greater only in the transition phase serving to trigger the steam detector. The more rapid rise in temperature of the foodstuffs necessarily contributes to a better preservation of the vitamins.
Compared with an appliance continuously supplying the maximum power, the cooking duration remains identical in an appliance according to the invention, but the ejection of steam is less substantial in the second part of the cooking process when the foodstuffs have risen in temperature. Because of the lower rate of consumption of water in the second part of the cooking process, the possible cooking time of the appliance with a given initial supply of water is increased.
Advantageously, the steam production device has a main reservoir supplying the water reservoir associated with the heating means, this arrangement making it possible to obtain steam more rapidly and to more easily modulate the steam output between full power of the heating element and reduced power.
According to an advantageous provision notably facilitating the cleaning of the cooking enclosure, the steam production device is arranged in a heating base, and the cooking enclosure is removable with respect to the heating base.
Then, advantageously, the steam detector is disposed in the heating base. This arrangement facilitates the transmission of the information supplied by the steam detector in order to reduce the power of the heating means. This arrangement also facilitates the cleaning of the cooking enclosure.
Advantageously, the descending conduit is provided at least partly in a side wall of the cooking enclosure. This arrangement makes it possible to collect the steam in the top part of the cooking enclosure, after it has passed through the foodstuffs. As long as the foodstuffs absorb sufficient steam and the exhausts permit the discharge of the remaining steam, full power can be preserved. The result is a higher cooking speed.
Then, advantageously, the cooking enclosure has at least two removable cooking receptacles each containing a part of the descending conduit. This arrangement makes it possible to use one or more cooking receptacles.
Advantageously, the descending conduit is provided at least partly in the heating base. This arrangement simplifies the design of the cooking enclosure, the steam detector then being able to be arranged in the heating base.
Advantageously, to make it possible to discharge the condensates, the detector is disposed in a chamber connected to an outlet flowing towards the outside of the appliance.
Advantageously, the descending conduit is connected to the cooking enclosure by an inlet arranged lower than the exhaust or exhausts. This arrangement assists the discharge of the steam through the exhausts and makes it possible to delay the progress of the steam in the descending conduit.
Advantageously, the descending conduit is connected to the cooking enclosure by an inlet whose cross-section is greater than the sum of the cross-sections of the exhaust or exhausts. When the flow of steam becomes too great to flow completely through the exhaust or exhausts, this arrangement assists the progression of the steam in the descending conduit.
Advantageously, the descending conduit is connected to the cooking enclosure by an inlet arranged close to at least one of the exhausts. This arrangement reduces the range of flow of steam necessary for triggering the detector.
Then, advantageously, at least one of the exhausts is arranged at a distance from the inlet. It has been observed that this configuration makes it possible to reduce the steam flow threshold necessary for triggering the detector.
Then, advantageously, the ratio between the cross-section of the exhaust or exhausts arranged at a distance from the inlet and the cross-section of the exhaust or exhausts arranged close to the inlet is between 1.6 and 2.4. This arrangement makes it possible to obtain a relatively stable detection threshold.
Advantageously the exhaust or at least one of the exhausts is provided in a lid forming the top wall of the cooking enclosure. This arrangement assists the discharge of the steam through the exhaust or exhausts concerned.
Then, advantageously, the descending conduit has an inlet arranged lower than the exhaust or exhausts provided in the lid. This arrangement facilitates the production of the lid and conduit.
Then, advantageously, the cooking enclosure has a cooking receptacle in which at least one portion of the descending conduit is provided and the exhaust, or one of the exhausts, arranged close to the inlet forms an orifice able to fit on the top edge of said conduit when the lid is turned over on said receptacle. This arrangement improves the storage of the appliance.
Advantageously again, the inlet is formed by a top opening of the descending conduit and the top of the internal wall of the lid is concave as far as a rib interposed between the top of the lid and the exhaust, or one or the exhausts, the rib being arranged around the inlet when the lid closes off the cooking enclosure. This arrangement prevents condensates from falling into the descending conduit.
Advantageously, the ratio between the mean power delivered by the heating means during the initial phase of rise in temperature and the mean power delivered by the heating means after the triggering of the steam detector is greater than or equal to 1.5, and preferably greater than or equal to 2. This arrangement makes it possible to benefit from a shorter duration of rise in temperature.
According to another characteristic, an intermediate passage connects the cooking enclosure to the bottom chamber. In other words, the intermediate passage is arranged higher than the bottom chamber. The steam descends through the intermediate passage to the bottom chamber, the intermediate passage being able to be formed by one or more orifices in the wall of the cooking enclosure.
Advantageously, the exhaust or at least one of the exhausts connects the cooking enclosure to the outside through the intermediate passage. This arrangement improves the precision of the triggering of the detector. This is because a flow of steam escapes from the cooking enclosure to the outside, first of all passing through the intermediate passage and then through said exhaust or exhausts. When the output of steam becomes greater, the steam flow becomes turbulent. Some of the steam is then directed towards the bottom chamber in which the steam detector is disposed.
Then, advantageously, the cross-section of the intermediate passage is greater than 90% of the cross-section of the exhaust or exhausts. This arrangement facilitates the flow of some of the stream to the bottom chamber when the steam output becomes greater.
Advantageously again, the intermediate passage extends over a width greater than the width of said exhaust or exhausts. This arrangement also facilitates the flow of some of the steam to the bottom chamber when the output of steam becomes greater.
Advantageously, the intermediate passage is arranged in the top part of the cooking enclosure. The steam first of all having passed round the foodstuffs to be cooked before passing through the intermediate passage, the reduction in power of the heating element controlled by the detection of the steam occurs when the entire cooking enclosure and its content are saturated with steam. This arrangement reduces the duration of cooking, since the maximum power of the heating means is kept as long as possible. Compared with an identical appliance of maximum power, in which the maximum power is kept throughout the cooking, the cooking performance is identical but the total energy consumed is less and the discharge of steam out of the cooking enclosure is manifestly reduced.